U.S. patent application number 13/949867 was filed with the patent office on 2013-11-21 for dsm enabling of electro mechanically controlled refrigeration systems.
This patent application is currently assigned to General Electric Company. The applicant listed for this patent is General Electric Company. Invention is credited to John K. Besore.
Application Number | 20130305749 13/949867 |
Document ID | / |
Family ID | 45695312 |
Filed Date | 2013-11-21 |
United States Patent
Application |
20130305749 |
Kind Code |
A1 |
Besore; John K. |
November 21, 2013 |
DSM ENABLING OF ELECTRO MECHANICALLY CONTROLLED REFRIGERATION
SYSTEMS
Abstract
An energy saving defrost control system for reducing power
consumption of an electromechanically controlled refrigerator is
provided. The system includes a defrost timer configured to control
a compressor according to an established run time, a defrost heater
control operatively connected to the defrost timer and configured
to activate a defrost heater in response to a timeout by the
defrost timer, a DSM module responsive to demand state signals from
an associated utility indicative of at least a peak demand and off
peak demand state, and a time delay latching relay comprising a
timer and configured to switch to one of a low position and a high
position based on the demand state signal.
Inventors: |
Besore; John K.; (Prospect,
KY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
General Electric Company |
Schenectady |
NY |
US |
|
|
Assignee: |
General Electric Company
Schenectady
NY
|
Family ID: |
45695312 |
Appl. No.: |
13/949867 |
Filed: |
July 24, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12951451 |
Nov 22, 2010 |
|
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|
13949867 |
|
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Current U.S.
Class: |
62/80 ;
62/155 |
Current CPC
Class: |
F25D 2600/02 20130101;
F25D 21/006 20130101; F25D 21/06 20130101; F25D 29/00 20130101 |
Class at
Publication: |
62/80 ;
62/155 |
International
Class: |
F25D 21/06 20060101
F25D021/06 |
Claims
1. An energy saving defrost control system for reducing power
consumption of an electromechanically controlled refrigerator,
comprising: a defrost timer adapted to control a compressor
according to an established run time; a defrost heater control
operatively connected to said defrost timer and configured to
activate a defrost heater in response to a timeout by said defrost
timer; a DSM module responsive to demand state signals from an
associated utility indicative of at least a peak demand and off
peak demand state; a time delay latching relay having a timer and
configured to switch to one of a low position and a high position
based on the demand state signal.
2. The system according to claim 1, wherein said time delay
latching relay further includes first and second contacts
configured to open when said relay is at a low position.
3. The system according to claim 1, wherein said first and second
contacts are configured to close upon switching to the high
position.
4. The system according to claim 1, wherein said DSM module is
configured to switch said time delay latching relay to the low
position based on a signal indicative of a peak demand period.
5. The system according to claim 4, wherein the defrost cycle is
disabled when said first and second contacts are open.
6. The system according to claim 5, wherein said defrost cycle is
configured to remain disabled until the relay is switched to the
high position.
7. The system according to claim 6, wherein said time delay
latching relay is configured to switch to said high position in
response to a timeout by said time delay latching relay timer.
8. The system according to claim 1, wherein said time delay
latching relay is a single throw, double pole relay.
9. A method for reducing power consumption of an electronically
controlled refrigeration system by disabling a defrost cycle during
periods of peak demand, said method comprising: controlling a
compressor according to the established run time of a defrost
timer; activating a defrost heater in response to a timeout by said
defrost timer, wherein said activation initiates a defrost cycle;
operatively associating a DSM module with said defrost timer,
wherein said DSM module is responsive to demand state signals from
an associated utility indicative of at least a peak demand and
off-peak demand state; providing said DSM module with a time delay
latching relay with first and second contacts; and switching said
time delay latching relay into one of a high and low position based
on the signal indicative of a peak demand period.
10. The method according to claim 9, further including switching
said time delay latching relay into a low position in response to a
signal indicative of a peak demand period.
11. The method according to claim 10, wherein switching said relay
into the low position opens the first and second contacts.
12. The method according to claim 11, wherein opening said contacts
pauses said defrost tinier and disables the defrost cycle.
13. The method according to claim 12, wherein said defrost cycle
remains disabled until said time delay latching relay switches back
to the high position.
14. The method according to claim 13, further including switching
said time delay latching relay to the high position in response to
a timeout by the time delay latching relay time.
15. The method according to claim 9, further including receiving a
signal indicative of a peak demand period while a defrost cycle is
in progress and switching said time delay latching relay to the low
position to suspend the defrost cycle.
16. A DSM enabled defrost control system capable of reducing peak
power consumption in an electromechanically controlled
refrigeration system, said defrost control system comprising: a
defrost timer operatively associated with a compressor, said
compressor configured to operate said defrost timer according, to
an established run time; a defrost heater control configured to
activate and deactivate a defrost heater based on said compressor
run time; a DSM module associated with said defrost timer and
responsive to demand state signals from an associated utility
indicative of at least a peak demand and off peak demand state; a
time delay latching relay having first and second contacts, wherein
said DSM module is configured to switch said time delay latching
relay to one of a high and low position based on the demand
state.
17. The defrost control system according to claim 16, wherein said
DSM module is configured to switch said time delay latching relay
to the low position based on s signal indicative of a peak demand
state.
18. The defrost control system according to claim 16, wherein said
first and second contacts are configured to open when said time
delay latching relay is in the low position.
19. The defrost control system according to claim 18, wherein the
defrost cycle is disabled when said first and second contacts are
open.
20. The defrost control system according to claim 16, said time
delay latching relay includes a timer configured to of time out
after a period of time and automatically return the relay to the
high position.
21. The defrost control system according to claim 20, wherein said
period of time is about 4 hours.
22. The defrost control system according to claim 16, wherein said
time delay latching relay is configured to switch to the high
position in response to a signal indicative of a non-peak demand
period.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of prior U.S. patent
application Ser. No. 12/951,451, filed Nov. 22, 2010, which is
hereby incorporated by reference in its entirety.
BACKGROUND OF THE DISCLOSURE
[0002] This disclosure relates to energy management, and more
particularly to energy management of household refrigeration
appliances. The disclosure finds particular application to adapting
electromechanically controlled refrigerators for operation in home
energy management systems.
[0003] Many utilities are currently experiencing a shortage of
electric generating capacity due to increasing consumer demand for
electricity. Currently utilities charge a flat rate, but with
increasing cost of fuel prices and high energy usage at certain
parts of the day, utilities have to buy more energy to supply
customers during peak demand, which causes prices to rise during
these times. If peak demand can be lowered, then a potential huge
cost savings can be achieved and the peak load that the utility has
to accommodate is lessened. In order to reduce high peak power
demand, many utilities have instituted time of use (TOU) metering
and rates which include higher rates for energy usage during
on-peak times and lower rates for energy usage during off-peak
times. As a result, consumers are provided with an incentive to use
electricity at off-peak times rather than on-peak times and to
reduce overall, energy consumption of devices at all times.
[0004] To take advantage of the lower cost of electricity during
off-peak times, systems have been provided that can automatically
operate power consuming devices during off-peak hours in order to
reduce consumer's electric bills and also to reduce the load on
generating plants during on-peak hours. Active and real time
communication of energy costs of devices to the consumer enables
informed choices of operating the power consuming functions of the
devices. Although these systems are capable of being run
automatically according to demand period, a user may choose to
override the system and run a device normally, or delay the
operation of the system for a particular period of time.
[0005] One method for providing low-cost reduction of peak and
average power is to implement a simple demand side management "DSM"
control device, also known as a smart appliance module "SAM", in an
existing electromechanical appliance that will adjust, or disable
power consuming elements to reduce maximum power consumption.
However, such a DSM/SAM add-on device will generally cut off the
power to an entire appliance. Therefore, there exists a need for
reducing peak power consumption without extinguishing all power to
the appliance.
[0006] Electronically controlled refrigerators generally include a
microcomputer that has control over various functions of the
appliance, such as temperature set point for example, to which can
be programmed to provide an appropriate DSM/SAM response. For
example, when a utility transmits a signal corresponding to a peak
demand period, the microcomputer may block access to, or
temporarily shuts off, particular features, such as the quick
chill, quick thaw, or quick cool features that have associated fans
that require additional energy. In addition, or alternatively, the
microcomputer may adjust the temperature set point of the freezer,
allowing the freezer compartment temperature to increase slightly
until the peak demand period is over. At the conclusion of the high
rate period, the microcontroller resets the set point to the
original set point temperature. The microcontroller may
additionally delay a scheduled defrost if the defrost is set to
occur during a peak demand period.
[0007] While electronically controlled refrigerators can adjust
energy usage in response to a "high demand", many refrigerators
include less technically sophisticated controls that do not use a
microprocessor.
[0008] The subject application provides a system that enables
refrigerators that are not equipped with electronic controls to
effectively adjust energy usage in response to "high demand"
conditions.
SUMMARY OF THE DISCLOSURE
[0009] According to an embodiment of the present disclosure, an
energy saving defrost control system for reducing power consumption
of an electromechanically controlled refrigerator is provided. The
system comprises a defrost timer configured to control a compressor
according to an established run time, a defrost heater control
operatively connected to the defrost timer and configured to
activate a defrost heater in response to a timeout by the defrost
timer, and a DSM module responsive to demand state signals from an
associated utility indicative of at least a peak demand and off
peak demand state. The system also comprises a time delay latching
relay comprising a timer and configured to switch to one of a low
position and a high position based on the demand state signal.
[0010] According to another embodiment of the present disclosure, a
method for reducing power consumption of an electronically
controlled refrigeration system by disabling a defrost cycle during
periods of peak demand. The method comprises controlling a
compressor according to the established run time of a defrost
timer, activating a defrost heater in response to a timeout by the
defrost timer, wherein the activation initiates a defrost cycle,
and operatively associating a DSM module with the defrost timer,
wherein the DSM module is responsive to demand state signals from
an associated utility indicative of at least a peak demand and
off-peak demand state. The method further comprises providing said
DSM module with a time delay latching relay with first and second
contacts, and switching the time delay latching relay into one of a
high and low position based on the signal indicative of a peak
demand period.
[0011] According to yet another embodiment of the present
disclosure, a DSM enabled defrost control system capable of
reducing peak power consumption in an electromechanically
controlled refrigeration system is provided. The defrost control
system comprises a defrost timer operatively associated with a
compressor configured to operate the defrost timer according to an
established run time, and a defrost heater control configured to
activate and deactivate a defrost heater based on the compressor
run time. The system further comprises a DSM module associated with
the defrost timer and responsive to demand state signals from an
associated utility indicative of at least a peak demand and off
peak demand state, and a time delay latching relay comprising first
and second contacts. The DSM module is configured to switch said
time delay latching relay to one of a high and low position based
on the demand state.
[0012] Still other features and benefits of the present disclosure
will become apparent from reading and understanding the following
detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 illustrates an exemplary embodiment of an energy
management system for household appliances;
[0014] FIG. 2 illustrates an exemplary prior art cold control
device;
[0015] FIG. 3(a) illustrates a refrigerator temperature management
system comprising a dual cold control configuration in accordance
with another aspect of the present disclosure;
[0016] FIG. 3(b) illustrates an exemplary wiring diagram for the
dual cold control configuration of FIG. 3(a);
[0017] FIG. 4 illustrates a refrigerator temperature management
system comprising a heated bourdon tube in accordance with another
aspect of the present disclosure;
[0018] FIG. 5 illustrates a refrigerator temperature management
system comprising a heated bourdon tube in accordance with yet
another aspect of the present disclosure;
[0019] FIG. 6 illustrates a refrigerator temperature management
system comprising a multiple tension counter spring in accordance
with yet another aspect of the present disclosure;
[0020] FIG. 7(a) illustrates a wiring diagram of a standard defrost
circuit for electromechanical control in accordance with yet
another aspect of the present disclosure; and
[0021] FIG. 7(b) illustrates a schematic of DSM module defrost
cycle control in accordance with yet another aspect of the present
disclosure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] An exemplary embodiment of an energy management system for
household appliances 100 is illustrated in FIG. 1. An electronic
controller 102 is provided for communicating with a utility meter
and reducing power consumption in response to a signal 106
indicative of a peak demand period. Electromechanically controlled
refrigerators, according to one aspect of the present disclosure,
include a cold control 120 to control the temperature of the
refrigerator compartments, which is depicted in FIG. 2. A cold
control 120 is a temperature control incorporating a single pole,
single throw switch with an associated set of electrical contacts
for turning a refrigerator's compressor and fans concurrently on
and off. A bourdon tube 122 is associated with the cold control 120
to sense temperature increases and decreases in a refrigerator
compartment. As introduced above, a bourdon tube 122 is a hollow
tube filled with refrigerant or an inert gas and placed in the
airstream of the compartment to be controlled. One end of the tube
connects into the back of the cold control 120 and includes a
diaphragm seal. The diaphragm seal is intimately associated with
the counter spring located on one side and a pressurized gas on the
other side of that seal. The other end of the bourdon tube 122 is
positioned in the compartment of the refrigerator to be controlled
that that is indicative of the ambient temperature of the
compartment.
[0023] For example, under normal conditions, it is desirable to
maintain the temperature of the freezer in a domestic refrigeration
appliance at 0.degree. F., plus or minus a few degrees. Therefore,
the cold control for the freezer would be calibrated such that the
center setpoint position of the selector would provide a freezer
compartment at 0 degrees F. If the user selects the 0 degree F. set
point, the cold control would cycle the compressor to maintain the
temperature in the freezer at approximately 0 degrees F. The
bourdon tube located in an area of the freezer senses the
temperature in its vicinity and if the temperature rises 1.degree.
or 1.5.degree., the pressure in the bourdon tube also rises, which
causes the bourdon tube to expand and overcome the counter spring
located on the other side of the diaphragm seal. By overcoming the
counter spring, a contact is tripped to activate the compressor.
The compressor will remain activated until the temperature in the
freezer returns to the selected set point of 0.degree. F., or other
set point as the user may select. In accordance with the decreasing
compartment temperature, the pressure in the bourdon tube also
decreases and causes the counter spring to overcome the bourdon
tube pressure acting on the diaphragm and open the contacts to
deactivate the refrigeration system.
[0024] The cold control 120 includes an input selector, typically a
rotatable shaft with a knob, for manually selecting the temperature
set point. Adjusting the angular position of the shaft in one
direction or the other alters the spring loading on the diaphragm
seal, which follows to alter the selected setpoint temperature.
Typically, the control is calibrated such that when the knob is at
its center point, the set point temperature is the temperature at
the midpoint of the selectable setpoint range, which for a freezer
cold control is approximately 0.degree. F. As the knob is rotated,
the selected setpoint temperature is shifted up or down relative to
the calibration point within established limits.
[0025] The system described herein adapts the above-described cold
control for use with a DSM control module of an energy management
system. With reference to FIG. 3(a), an illustrative embodiment is
provided that includes two cold control devices, cc1 and cc2,
supported on a common mounting plate 130, each with a separate
bourdon tube 122(a), (b) and separate switches 125 and 126, each
comprising a control knob shaft 133(a) and 133(b) respectively for
manually adjusting the set point for its associated switch. The
shafts 133(a) and 133(b) of the two switches 125 and 126 are
mechanically linked by belt 134 for rotation together. Shaft 133(b)
has attached thereto a user adjustable knob (not shown). By this
arrangement, user rotation of the knob rotates both shafts
concurrently thereby adjusting the setpoint of each control by the
same amount. That is, user rotation of the control knob changes the
setpoint of each control by the same number of degrees relative to
their respective calibration setpoint temperatures. While the
linkage illustrated in FIG. 3(a) is a belt, it is to be understood
that any mechanical linkage operative to cause rotation together
could be similarly employed, such as for example a gear train.
[0026] The bourdon tubes 122(a)(b) are attached to cold controls
cc1 and cc2 such that they run parallel to each other with each
tube located in the same compartment and are sensing the same
temperature. The first cold control cc1 is calibrated to provide a
first specific calibration temperature set point, as the midpoint
setting for the control shaft. The second cold control cc2 is
calibrated to provide a second calibration temperature set point
different from the first at the midpoint setting for its control
shaft. In the illustrative embodiment, the first calibration set
point temperature is set at 0.degree. F., and the second
calibration setpoint temperature is set to a higher temperature of
0.degree. F. As illustrated schematically in FIG. 3(b) the cold
control switches 125 and 126 are electrically connected in
parallel. The parallel combination is connected in series with the
compressor. A DSM controlled switching, device R1, is provided in
series with the cold control switch comprising the lower
calibration set point, which in the illustrative embodiment is
switch 126, to selectively shift the lower set point control (cc2)
in and out of the circuit. When the lower calibration set point
control is in the circuit, even though both controls are
operatively connected, the lower calibration setpoint control will
always be controlling because the lower setpoint will always be
exceeded first. When the lower setpoint control is shifted out of
the circuit, operation of the compressor will be controlled by the
higher calibration setpoint control. By this arrangement, opening
the DSM controlled switching device R1, for example in response to
a peak demand signal from a utility, increases the effective
setpoint temperature for the compartment by the delta in
calibration setpoints. In the illustrative embodiment this delta is
chosen to be 6 degrees F. However other values could be similarly
employed depending on the desired reduction in energy usage when
operating the refrigerator in an energy saving mode. The DSM
controlled switching device R1 is opened and closed in response to
a signal from an associated DSM module, which receives a demand
signal from an associated utility. When the signal indicates a peak
demand period, the switch is opened, enabling control of the
compressor by the second cold control and raises the selected set
point temperature by 6.degree. F. In contrast, when the signal
indicates a non-peak demand period, the DSM controlled switching
device R1 is closed, thus maintaining control by the first cold
control. In the illustrative embodiment, the DSM controlled
switching device R1 is an electromechanical relay device,
preferably a single pole, single throw relay device. However,
electronic switching devices could be similarly employed.
[0027] When the DSM module indicates a period of peak demand, the
binary output of the DSM module will drive the DSM controlled
switching device R1 to open, causing the system to enter energy
savings mode and allowing only cc1 to control. Since cc1 has mid
set point of 6.degree. F., the refrigerator will now cycle around
the 6.degree. F. set point+/-hysteresis. At the conclusion of the
peak demand period. R1 is driven to close and the system returns to
normal mode, wherein the cc2 commands control, returning, the
refrigerator set point to 0.degree. F.+/-hysteresis. There will be
a limit on how warm a user can calibrate cc1, and there will be a
max temperature the user is allowed to dial in. Therefore, the
warmest possible setting of the cold control available to the user
will need to coincide with this maximum allowable setpoint for food
preservation criterion. This ensures that a compartment does not
get too warm during a peak demand period and ruin any contents
therein.
[0028] Although the system described herein is discussed mainly in
terms of controlling the temperature in a refrigerator freezer, the
system may alternatively or simultaneously be implemented into the
fresh food compartment of a refrigerator and other refrigerated
devices controlled by electromechanical cold controls described
herein, for example a wine chiller, with set point temperatures
adjusted within the limits of the acceptable performance limits of
the said device. In the refrigerator example, the fresh food and
freezer systems may be independent from each other or interrelated,
such that shifting the freezer temperature set point also shifts
the temperature set point in the fresh food compartment by a
comparable degree.
[0029] In an alternative embodiment, the same dual tier selectable
temperature control concept is achieved, however with only one cold
control device, rather than two separate cold control devices, as
provided above. As best seen in FIG. 4, a heating element 140 is
applied to the bourdon tube 122 to add a metered amount of heat to
the tube to mimic a higher temperature. The heating element 140 may
consist of an insulated nickel chrome wire heater that is coiled
around the bourdon tube. A DSM switching device R1, similar to that
provided above is employed and is controlled by a DSM module 144 to
enable or disable the heating element 140. As with the scenario
above, the cold control 120 is calibrated to a desired set point
temperature with heat present from the heating element 140. The
wattage of the heater is selected to effectively offset the control
calibrated, set point by a predetermined amount.
[0030] In one illustrative example, an insulated nickel chrome wire
is coiled around a bourdon tube 122, which is connected to a single
pole, single throw relay R1. The relay R1 is generally closed to
enable the heater to deliver a very low calibrated wattage of heat
to the bourdon tube 122. During a peak demand response, binary
output from the DSM module 144 opens the DSM switching device R1
de-energizing the heating element 140. Without the heat from the
heating element, the cold control 120 responds to the actual
temperature in the compartment rather than a temperature that is
offset by the heater, which has the effect of increasing the
effective setpoint temperature by an amount determined by the
wattage of the heater. In the illustrative embodiment, the wattage
of the heater is selected to provide the desired effective increase
of 6 degrees F., which is achieved with a minimal wattage heater.
This wattage will be dependent on the design of the cold control,
specifically the nature of the inert gas as well as the stiffness
of the diaphragm spring. Therefore, the refrigerator's compressor
and fans will be controlled to a setpoint temperature, which is 6
degrees higher than the user selected setpoint, until the peak
demand period is over and the DSM module 144 closes the switching
device and enables the heater once again, restoring the selected
setpoint temperature as the effective setpoint temperature.
[0031] According to another aspect of the present disclosure, the
heating means for the bourdon tube 122 is provided by a heat pipe
150 that extends from within the fresh food section (temperature of
between approximately 37-44.degree. F.) to add heat to the bourdon
tube 122 that is exposed to freezer airflow, cycling at
approximately 0.degree. F. The heat pipe 150 acts as a conductive
pipe that resides in the fresh food compartment. Since the fresh
food compartment is typically at least about 37.degree. F. and
always significantly warmer than the Freezer, the pipe 150 will
naturally conduct heat into the bourdon tube 122. If the heat pipe
150 is thermally connected to the bourdon tube 122 at all times,
the offset is present continuously.
[0032] As best illustrated in FIG. 5, a moveable heat block 152 is
provided and attached to the bourdon tube. The heat block includes
an upper portion 152(a) and lower portion 152(1)), with the lower
portion 152(b) in contact with the heat pipe 150 and insulated from
the freezer air, and the upper portion 152(a) is soldered to the
bourdon tube 122. The lower portion 52(b) is moveable, such that it
may be shifted to meet the upper portion heat pipe 150 to engage
and disengage the heat flow along the heat pipe 150. As
hereinbefore described with respect to the heater, the cold control
120 is calibrated with the heat block 152 engaging the heat pipe
150, such that the heat pipe is conducting heat into the bourdon
tube 122 to deliver heat at a predetermined wattage level from the
heat pipe 150. A DSM switching device R1 is driven by a DSM module
144, such that output from the DSM module 144 can cause the
switching device R1 to energize or de-energize an associated
solenoid 154. When energized, the solenoid 154 shifts the lower
heat block portion 152(b) closer to the upper heat block portion
152(a) to enable heat flow along, the heat pipe 150, through the
heat blocks and to the bourdon tube 122. Other arrangements for
shifting the conductive block may also be provided, such as a
stepper motor, or the like. During a peak demand period, the
switching device R1 opens to de-energize the solenoid 154 and cause
the lower moveable heat block portion 152(b) to move away from the
upper portion 152(a) and cut off the heat flow to the bourdon tube
122. Without the heat from the heat pipe, the cold control 120
responds to the actual temperature in the compartment rather than a
temperature that is offset by the heat from the heat pipe, which
has the effect of increasing the setpoint temperature by an amount
determined by the amount of heat provided by the heat pipe when not
disengaged. At the conclusion of the peak demand period, the DSM
switching device R1 will close energizing the solenoid 154, which
moves the lower heat block portion 152(b) back to engage the upper
heat block portion 152(a) to return heat flow to the bourdon tube
122 restoring the effective setpoint for the control to the
selected setpoint.
[0033] According to another embodiment of the present disclosure, a
means of achieving a dual tier selectable set point may include
equipping a cold control device 120 with multiple spring tension
positions. Referring back to FIG. 2, a cold control comprises
housing and a metal snap at the bottom where the bourdon tube comes
in. The end of the bourdon tube that meets the cold control housing
includes an elastomeric diaphragm 160, which is intimately
associated with a counter spring 162 that is mounted to the
housing. The spring includes two ends, one that is mounted against
the housing and one that rests against the diaphragm 160. This
counter spring 162 delivers a constant spring force against the
diaphragm 160 to counter the back pressure on the opposite side of
the diaphragm 160 emanating from the bourdon tube 122. The spring
tension determines the cold control's temperature set point.
[0034] As best illustrated in FIG. 6, the cold control 120 includes
internal modifications, such that the counter spring 162 may
provide varied levels of back pressure (force) against the gas
pressure of the bourdon tube 122 and effectively shift the
calibration point of the cold control 120 on demand. The levels can
be achieved by several means, such as electromagnetic shifting of
the spring base, a platen, or any other means of physically
shifting the spring base upon command to deliver a new spring
position resulting in a different force to counter the bourdon tube
internal pressure. For instance, in terms of a platen, an actuator
164 may be included to shift the platen on the back side of the
counter spring 162 from position A to position B, which changes the
spring force, thereby changing the control set point from 0.degree.
F. to 6.degree. F. Alternatively, the platen may shift the spring
numerous times to a variable number of positions representing, a
variable array of temperature setpoint shifts. For instance,
position C could represent 0.degree. F. position B could represent
3.degree. F., and position A could represent 6.degree. F.
Accordingly, one could choose to what degree the mechanical cold
control was to shift its temperature set point, such as in the case
of a medium demand period, cold control could only shift to about
3.degree. F., rather than to about 6.degree. F. In the case of
multiple setpoints or positions, some means of multiple indexing,
beyond two positions would be required to position the platen at
any one of the available positions. This could be achieved with
numerous mechanical systems known to those skilled in the art. One
example includes a stepper motor driven by multiple relays or by
rotary cams that would shift the platen based on a variable voltage
input to a stepper motor. The stepper could be indexed each time
the relay pulses a voltage input to the motor. Various cam, motor,
and linkage combinations known to those skilled in the art could be
employed. Ultimately, the movement of the platen is controlled by
the DSM switching device R1, implemented in a similar manner as
described above. The DSM switching device R1 is controlled by the
DSM module to engage or disengage the drive mechanism for the
platen (or other spring shifting means). This shifting may be
manually disabled by a user when higher set points are
undesirable.
[0035] In addition to adjusting the temperature set point of a
refrigerator compartment, another circuit described herein and
exemplarily illustrated in FIG. 7(a), may be used to disable or
suspend the defrost cycle of a refrigerator during a peak demand
period. In a non-DSM enabled electromechanically controlled
refrigerator, an automatic defrost cycle is typically performed
when the cumulative compressor run time reaches a predetermined
total run time for example sixteen hours, which is established by
the design of the defrost timer 170. This can be achieved using a
timer actuated defrost heater control that controls the time
between defrost cycles, the interval time, and the duration of the
defrost cycle, the defrost time. Timer 170 is configured to turn on
the defrost heater 174 when the interval timer times out. When the
cold control 172 is satisfied or turns the system off, the timer
motor 182 stops. By this arrangement, the defrost timer motor 182
initiates a defrost cycle every time the interval timer times out,
such as in the above example, every sixteen hours of compressor run
time. When it is time for defrost, the timer switch engages contact
B, which enables energization of defrost heater 174 and switches
the cold control 172 out of the circuit, thereby preventing it from
comprising any control function relative to the cooling system or
fans. The cooling system and fans will be disabled as long as
contact B is engaged. Contact B will remain engaged until the
defrost timer times out. In the illustrative embodiment, the
defrost heater "on-time" is on the order of 20 minutes When the
defrost duration timer times out, contact A will close, triggering
the refrigeration system and fans to restart and return the system
control to the cold control 172. The defrost interval timer will
begin counting down until the next defrost period.
[0036] The timer motor 182, which advances the timer, runs only
when the refrigerator cold control 172 is energized and calling for
cooling from the refrigerator compressor. The defrost cycle is
terminated in this non-DSM refrigerator when the defrost timer
advances beyond the design defrost time or the defrost termination
thermostat 176 opens due to a specified temperature being reached
in the evaporator.
[0037] In the case of the DSM enabled electromechanical
refrigerator and with reference to FIG. 7(b), a DSM controlled
defrost switch is provided that comprises in the illustrative
embodiment, a time delay latching relay R2 with two sets of
contacts C1 and C2 that are serially placed in the voltage supply
circuit of the defrost timer motor and the defrost heater
respectively (FIG. 7(a)). According to this embodiment, R2 is
preferably a single throw double pole relay which toggles between a
first state in which contacts C1 and C2 are closed, and a second
state in which contacts C1 and C2 are open. This relay incorporates
a time delay feature which limits the total length of time the
relay will remain "latched" in the second state. Once this delay
time elapses, the relay will return to the first state. When the
relay is in the first state with both sets of contacts closed in
positions D and F (FIG. 7(a)), the defrost cycle operates normally.
When the relay is switched to its second state with both sets of
contacts open in positions C and F (FIG. 7(a)), the defrost cycle
is disabled until at least one of two events occur: 1) the relay
time delay latching relay R2 is switched to its first state by the
DSM Module toggling the input because a peak demand period has
concluded, or 2) the time delay latching relay R2 "times out" and
switches the relay to its first state. Those skilled in the art of
time delay latching relays will appreciate the circuitry inherent
to a relay system that latches and starts a timer and remains
latched until the relay "times out" or the input to the relay is
toggled.
[0038] Without a time delay feature added to the relay, the DSM
module would disable a defrost by way of contacts C1 and C2 for the
entire length of time that the utility allotted for the demand
response event. The defrost cycle would be disengaged until the
utility pricing returned to a low cost state. While such suspension
provides desirable energy reduction, suspension of defrost for a
prolonged period may result in an undesirable build up of frost on
the evaporator. To avoid such an occurrence, in the embodiment of
the energy saying defrost control system of FIG. 7(a), the time
delay relay R2 limits the length of time the defrost cycle can be
delayed to the duration of the time delay period of the relay. A
typical time delay period would be about four hours, since most
utilities invoke demand response high or critical events for a 4
hour maximum elapsed time. Obviously, this timeout period could be
set to any desired timeframe as controlled by the time delay built
in to the timer. If set too long, the refrigerator would be at risk
for over-icing, of the evaporator in areas with high humidity and
numerous door openings.
[0039] The DSM module is configured to switch relay R2 to its
second state on receipt of a signal indicating the beginning of a
peak demand state or high rate period, and to return the relay to
its first state on receipt of a signal signifying the return to an
off peak state of the end of the high rate period. For example,
when a DSM high price event occurs, the DSM module 144 drives the
time delay latching relay R2 to open contacts C1 & C2. By so
doing, the defrost timer motor 182 is halted such that a defrost
cannot be initiated in the future until the DSM module returns the
relay to its first state, which occurs either at the end of the DSM
event or the time delay inherent to the time delay latching relay
is satisfied. Also, if a defrost is already underway when the DSM
event occurs, the opening of contact C2 will terminate the defrost
until the event is over or until the time delay latching relay
timer "times out" and returns the system back to normal, i.e.,
unlatches the relay.
[0040] The invention has been described with reference to the
preferred embodiments. Obviously, modifications and alterations
will occur to others upon reading and understanding the preceding
detailed description. It is intended that the invention be
construed as including all such modifications and alterations.
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